阀体锻压成形过程的计算机模拟分析

阀体作为石油开采的重要零部件,对其性能的要求也较高,传统阀体的制造大多采用铸造,存在成本高,精度低以及性能差的缺陷,采用锻压方式制造的阀体,精度高,成本低以及质量好,为此利用有限元仿真软件DEFORM-3D实现阀体锻压成形过程的数值模拟,在应力、应变分布、载荷计算和材料流动速度等方面做了深入研究,分析了阀体锻压过程中的参数选择,可以为模具及成形设备的设计提供依据。     

大型钢锭加热过程数值模拟与验证

对重量为44t的大型钢锭的锻前加热过程进行了数值模拟分析.介绍了钢锭的结构尺寸、材料的热物性参数以及数值模拟所需的边界条件,模拟得到了加热过程中钢锭的升温曲线.在加热过程中对钢锭内部温度进行了测量,结果表明模拟结果与实测结果基本吻合.     

中厚板轧制过程中轧制力变化有限元模拟

采用动态显式有限元法对中厚板轧制过程进行了分析.分析了轧制过程稳定阶段接触区中厚板单元数、轧辊单元尺寸以及中厚板初始速度选择对有限元分析计算结果的影响,得出了合理的轧制过程有限元模拟参数,并对某中厚板厂15道次轧制过程轧制力变化规律进行了分析,稳定阶段轧制力计算结果与实测结果非常接近.该结果对中厚板轧制过程模拟具有一定的参考意义.     

钢轨万能精轧过程的三维弹塑性有限元模拟

借助有限元分析软件MSC.Marc,采用三维热-机耦合弹塑性有限元模型,对钢轨万能精轧过程进行模拟分析。以UR-EF-UF三机架连轧过程为研究对象,建立变形过程优化模型。将轧件尺寸模拟结果与实验结果进行比较,两者吻合较好,验证了模型的准确性。对轧件变形过程、轧制接触状态、应力应变分布以及速度变化等模拟结果进行了讨论分析,揭示了万能轧机各道次的加工特点和轧件在连轧变形过程的变形规律。     

铁素体区热轧带钢温度场的数值模拟

为了优化轧制工艺和提高最终产品的质量,通过对轧件轧制过程传热关系的分析,采用软件ANSYS对低碳钢带铁素体区轧制过程温度场进行了模拟,得到了连轧过程的温度场数学模型,模拟结果与现场实测值吻合.     

大型锻件热处理过程的数值模拟研究

在对大型锻件传热分析的基础上,建立了大型锻件的物理模型,对其温度场的变化规律进行了模拟计算,同时将模拟结果和实验结果进行了对比分析,并通过实例说明了热处理过程数值模拟方法的准确性和优越性,为进一步分析此类工件的组织转变和应力应变等奠定了基础.     

中厚板轧后冷却过程中温度场的数值模拟

在分析中厚板轧制各阶段冷却过程的基础上,用有限差分法对中厚板轧后冷却过程的温度场进行了模拟数值求解,得到了钢板在水冷状态下的温降曲线和瞬时温度场分布,并进行了实验验证.实验验证表明,模拟结果与实测结果基本符合,为制定合理的控冷工艺提供了依据.     

大型船用曲轴曲拐弯锻过程的计算机模拟与工艺优化研究

采用计算机模拟和试验手段研究了传统工艺曲拐弯锻的过程,指出了传统工艺的不足和锻造过程容易出现的各种典型缺陷。采用逆推法确定了改进工艺后预成形毛坯形状,优化了毛坯的形状因子,有针对性地提出了解决各种缺陷的措施。在此基础上对改进的工艺进行了计算机模拟,模拟结果表明,改进后的工艺能够消除喇叭口、裂纹、“细腰”、减薄等缺陷;毛坯变形抗力为传统工艺的72％;毛坯截面积减小,可节省原材料约15％。最后对改进的工艺进行了试验,得到了合格的曲拐毛坯锻件,验证了模拟的准确性。所建立的模型和研究方法为进一步优化锻压工艺和今后开发其它型号的大型曲轴曲拐产品提供理论指导和技术保障。     

大圆钢轧制三维塑性变形有限元模拟

使用ANSYS/LS-DYNA通用有限元分析软件对大圆钢轧制过程进行了模拟仿真,得到了采用单圆弧成品前椭圆孔型的大圆钢轧制的等效应力场、等效应变场,分析了轧件横截面的等效应变和等效应力分布情况.成品前孔型改为双圆弧椭圆孔型后重新模拟轧制过程,把模拟结果进行比较,得出采用双圆弧成品前椭圆孔型有利于改善成品道次的应力、应变分布.     

铝板坯充型过程流场与温度场的耦合数值模拟

利用FLOW-3D软件对铝的充型过程进行了数值模拟,采用了耦合模拟的方法对结晶器内的流场和温度场进行了分析.通过比较不同的换热系数和浇铸速度下的结果,得到换热系数和浇铸速度对结晶器内流场和温度场的影响.     

CSP线高强度细晶热轧板的混晶和变形拉长晶粒的成因

对CSP线生产的高强度细晶热轧板的混晶和拉长晶粒的成因进行了分析,用有限元分析法模拟了热轧带钢的变形区的剪切应变场和温度场,用Gleeble实际模拟轧制工艺和组织变化。结果表明,CSP线高强度细晶热轧板的混晶和拉长晶粒的形成与钢板轧制过程中的钢板表层的变形场及温度场有关,也与先析出铁素体的形成后再进行轧制变形的过程有关;采用奥氏体深过冷轧制,既保证得到细晶粒又避免产生混晶和被变形拉长的晶粒。新的CSP轧制工艺,成功地生产了高强度高成形性细晶粒C-Mn热轧板。     

Simulation of aluminothermic smelting of Al-Zr and Al-Zr-Mo-Sn alloys

Aluminothermic smelting of Al-Zr and Al-Zr-Mo-Sn alloys has been simulated in terms of thermodynamics. The thermodynamic properties of molybdenum and zirconium intermetallic compounds are calculated. It is demonstrated that, with consideration for their formation, the calculated compositions of aluminothermic blends and the forecasted extraction of target metals into an alloy are in good agreement with the data obtained during pilot tests.     

Tensile and compressive stress in the metal around a corrosive nonmetallic inclusion,in the presence of an aqueous medium

The formation of a region where corrosive inclusions interact with metal in an aqueous medium is investigated. The inclusion expands as a result of hydration, and corresponding tensile and compressive zones are formed. On the basis of the results, the mechanical-stress distribution around hydrating inclusions is simulated.     

连铸坯表面横裂纹与材料高温断裂力学性能的关系

通过一种新的试验研究方法,即利用含缺口试样模拟铸坯表面横裂纹的产生过程,指出了材料高温断裂力学性能在研究连铸坯缺陷中的重要意义,并介绍了部分试验研究结果。     

Investigation of striation formation in thin stainless steel tube during pulsed Nd:YAG laser cutting process by numerical simulation

The formation of a striation pattern in a thin stainless steel tube was investigated by numerical simulation during a pulsed Nd:YAG laser cutting process. The simulated results were compared with the experimental results, which were performed under the same conditions for simulation. The simulated results showed good agreement with the experimental results. Although the formation of the striation pattern was influenced by various laser parameters, the laser power density had become the most important factor in the formation of striation patterns, since the laser power density is the most influential in the heating of metal, and the striation formation is caused by the ejection of molten metal and evaporation during laser cutting process. Although a high power density resulted in clear regular striation patterns, relatively low power density caused the formation of a hot spot, which hindered the formation of regular striation patterns and caused less striation. The numerical simulation calculations can be used to predict the shape of striation patterns and to offer a way to provide a smooth cut wall.     

Study of the Formation Mechanism of A-Segregation Based on Microstructural Morphology

A model that combines a cellular automaton (CA) and lattice Boltzmann method (LBM) is presented. The mechanism of A-segregation in an Fe-0.34 wt pct C alloy ingot is analyzed on the basis of microstructural morphology calculations. The CA is used to capture the solid/liquid interface, while the LBM is used to calculate the transport phenomena. (1) The solidification of global columnar dendrites was simulated, and two obvious A-segregation bands appeared in the middle-radius region between the ingot wall surface and the centerline. In addition, the angle of deflection to the centerline increased with the increasing heat dissipation rate of the wall surface. When natural convection was ignored, the A-segregation disappeared, and only positive segregation was present in the center and bottom corner of the ingot. (2) Mixed columnar–equiaxed solidification was simulated. Many A-segregation bands appeared in the ingot. (3) Global equiaxed solidification was simulated, and no A-segregation bands were found. The results show that the upward movement of the high-concentration melt is the key to the formation of A-segregation bands, and remelting and the emergence of equiaxed grains are not necessary conditions to develop these bands. However, the appearance of equiaxed grains accelerates the formation of vortexes; thus, many A-segregation bands appear during columnar–equiaxed solidification.     

小方坯中心缩孔的数值模拟分析

中心缩孔是铸坯质量缺陷中较难解决并且极易出现的问题。基于方坯连铸凝固末端中心缩孔形成的机理,建立1/4方坯二维热力耦合模型,应用ANSYS有限元软件进行模型分析,与传统热力耦合模拟过程进行了对比。结果表明,传统模型法模拟的中心缩孔的形成过程与实际不符,新模型法消除了传统方法的漏洞,模拟的中心缩孔形成的规律和经过理论分析所得中心缩孔形成的规律一致。并对铸坯温度和坯壳厚度变化进行了分析。     

Thermal distortion in copper moulds for continuous casting of steel: numerical study on creep and plasticity effect

In this work, the thermal distortion of a copper mould for continuous casting of steel is investigated through numerical models based on the finite element method. Special attention is devoted to the accuracy of the adopted material properties: several elasto-plastic models, with or without creep effects, are considered and compared into the analysis. The early formation of a bulge close to the meniscus is correctly simulated and results are in good agreement with experimental data from the literature.     

Primary radiation damage of an FeCr alloy under pressure: Atomistic simulation

The primary radiation damage of a binary FeCr alloy deformed by applied mechanical loading is studied by an atomistic molecular dynamics simulation. Loading is simulated by specifying an applied pressure of 0.25, 1.0, and 2.5 GPa of both signs. Hydrostatic and uniaxial loading is considered along the [001], [111], [112], and [210] directions. The influence of loading on the energy of point defect formation and the threshold atomic displacement energy in single-component bcc iron is investigated. The 10-keV atomic displacement cascades in a “random” binary Fe–9 at % Cr alloy are simulated at an initial temperature of 300 K. The number of the point defects generated in a cascade is estimated, and the clustering of point defects and the spatial orientation of interstitial configurations are analyzed. Our results agree with the results of other researchers and supplement them.     

Effect of Microstructure on High-Strength Low-Alloy Steel Welded Joint Toughness with Simulation of Heat-Affected Zone Coarse-Grained Area

Metallurgist - A simulated coarse-grained heat affected zone microstructure formation mechanism is established in high strength low alloy steels using electron backscatter diffraction (EBSD). The...